Color television reproduction tube



Jan. 8, 1952 D, A, JENNY COLOR TELEVISION REPRODUCTION TUBE 2SHEETS-SI-IEET 1 Filed March 1, 1950 11 in 1 3: is 4.

INVENTOR DIETRICHA. ITENNY QQE b Jan. 8, 1952 JENNY 2,581,487

COLOR TELEVISION REPRODUCTION TUBE Filed March 1, 1950 '2 SHEETS-SHEET 2i E. v "E. LLLLL WILL;

INVENTQR DIETRICH A. JENNY ATTO R N EY Patented Jan. 8, 1952 COLORTELEVISION REPRODUCTION TUBE Dietrich A. Jenny, Princeton, N. J.,assignor to Radio Corporation of America, a corporation of Delaware-Application March 1, 1950, Serial No. 147,034

This invention is directed to a cathode ray tube and specifically to asinglepicture tube for viewing television pictures in color.

This invention is directed to a television picture tube of the typewherein the electron beam of the tube is caused to approach the targetsurface from a direction having a slight angle to the normal of thetarget surface. Picture viewing tubes of this type may have directionaltype fluorescent screens which luminesce in different colored lightdepending upon the directional approach of the beam. One specific typeof directional screen is that formed of small elemental cells. the innersurfaces of which are coated with phosphor materials. The electron beamis caused to scan over such a cellular target surface and caused toimpinge upon the screensurface at an angle and tostrike the phosphorcoated inner surfaces of the individual cells. Such screens may be madeof two or more phosphor materials each fiuorescing with a differentcolored light upon impact by the beam. Such a screen structure is shownand described in the co-pending application to Schroeder Serial No.730,637, filed February 24, 1947, and in the'co-pending application toR. R. Law, Serial No. 143,405, filed February 10, 1950. 1 I

The last cited co-pending application also describes a color televisionpicture. tube usinga single electron gun. The electron beam, iscommutated into three portions and each portion is caused to approachthe cellular target structure at a different angle. Each beam portion iscaused to strikea different phosphor coated inner surface of each screencell, to produce luminescence in a color corresponding to the directionof approach of the electron beam.

The specific tube described in the above cited co-pending application toR. R. Law involves the use of a first rotating magnetic field forconically scanning the beam in a circle over the surface of an aperturedcommutator electrode. The portions of the beam penetrating through theaper- 'tured electrode are descanned by a second rotatapertures throughwhich an electron beam passes 8 Claims. (Cl. 3l3-76) at a specific angleto the masking electrode'surface. The beam continues on to strike aphos-" phor on a transparent support plate which emits light of aspecific color. When the electron beam passes through the apertures ofthe mask, at

another predetermined angle to the plane of the mask, the beam willstrike a second phosphor,- luminescing with a different colored light.Such tubes may utilize two or more beams, which are formed by individualelectron gun structures, or

such tubes may utilize a single electron beam, which is caused to strikethrough the apertured mask from the several different angular directionssuccessively. Such an electron picture tube is described in theco-pending application Serial No. 762,175, filed July 19, 1947, ofAlfred N. Goldsmith.

This last described directional target structure, 1

using a masking electrode, may be combined with the single gun picturetube disclosed in the abovecited co-pending application to R. R. Law,Serial No. 143,405, filed February 10, 1950.

It is an object of this invention to simplify the structure of a cathoderay picture tube using a directional type target electrode.

It is a further object of my invention to simpli fy the structure of acolor television picture tube using a single beam, which is rotatedabout its normal path to bring the beam into the target surface at anangle.

itself to converge to a fine spot at the target sur-. face, but also todirect the deflected beam back to its beam path and at an angle to thenormal of the target surface. The successful use of the deflecting andfocusing fields depends upon bringing the beam to, a cross-over orpoint. of focus within the deflecting field, and so that the virtualcross-over point imaged by the focusing field on the target isessentially on the axis of the focusing field.

The novel features which I believe to be char-' acteristic of myinvention are set forth with.

particularity in the appended claims, but the invention itself will bestbe understood by reference to the following description taken inconnection with the accompanying drawing, in which:

Fig. 1 is a sectional view of a cathode ray picture tube according to myinvention;

Fig. 2 is a partial enlarged view of the tube of Fig. 1;

Figs. 3 and 4 are partial sectional views of the screen structure usedin the tube of Fig. 1; and

Fig. 5 is a sectional view of a screen structure which may also be usedin the tube of Fig. 1. Figs. 1 and 2 show a cathode ray tube accordingto my invention. The tube consists of an evacuated envelope in, havingboth a conical portion l2 and a tubular neck portion i4 coaxially joinedtogether as shown. The conical portion l2 of the envelope is closed by aface plate It and closely spaced from it is a fluorescent target andscreen structure l8 to be described below. Mounted coaxially within thetubular envelope portion I4 is an electron gun structure for producingand focusing a beam of electrons 20 on the screen structure la. Theelectron gun is essentially a conventional design and consists of acathode cylinder 22 closed, as is shown, at the end facing the targetscreen l8. The closed end of the cathode cylinder is coated, as is wellknown in the art, by a mixture of strontium and barium oxides which,when heated to an appropriate temperature, produce a free emission ofelectrons.

A control grid cylinder 24 coaxially surrounds the electron emitting endof the cathode 22 and has an apertured plate structure closing one endthereof and closely spaced from the coated surface of the cathode. Ashield electrode or grid 26 constitutes a short thimble-like electrodehaving an aperture in the bottom thereof for the passage of electronstherethrough. Spaced along the tubular neck portion l4 and coaxial withthe other electron gun parts is a first anode electrode 28 constitutinga tubular member, having an enlarged portion at the end facing thefluorescent screen l8. A second anode electrode constitutes a conductivecoating 30 on the inner surface of the tubular envelope portion l4 andextends into the conical envelope portion l2 to a point adjacent thefluorescent screen 18. The several electrodes described, whichconstitute the electron gun structure of the tube, are. during tubeoperation, connected to a source of direct current potential which maybe a voltage divider 32 connected between the positive and negativepoints of a direct current potential source.

In a tube of the type shown in Fi 1. certain voltage ranges are appliedto the several electrodes to form an electron beam from the'thermionicemission of the cathode 22. The following voltages are given as anexample of operating potentials, which may be applied to the severalelectrode and are not meant to be limiting. In a successfully operatedtube of the type described. the control grid 24 was operated in a rangebetween and 60 volts below the potential of the cathode electrode.Screen grid electrode 28 was operated in the order of 100 volts positiveto cathode potential to provide a positive accelerating field fordrawing the thermionic emission from the cathode surface to the negativecontrol grid 24. First anode electrode 28 was operated at around 2,000volts positive relative to cathode potential, while second anodeelectrode 30 was maintained at around 12,000 volts positive, relative tocathode potential.

The electrostatic fields produced respectively between electrodes 28 and28, and 28 and 80, are of a converging nature and cause the electrons toform into a beam having a minimum cross section or cross-over point 56(Fig. 2) between tubular electrode 28 and screen l8. The electron beam,after passing through this cross-over point 56, tend to diverge beforestriking the screen l8. In order to redirect the electrons back to asecond cross-over point of minimum cross sectional area, a focusingfield is used to image the cross-over point 58 on the screen surface l8.Such a focusing field is obtained by the use of a coil 34 mounted on theneck portion l4. A soft iron casing 88 is used, as is .well, knownin,.the

art, t enclose coil 34, to restrict and intensify.

the focusing field of coil 34. Casing. 36 hasa, short air gap 38 toconcentrate the magnetic focusing field in a small transverse region ofthe, neck portion l4. As is well known in the. art,- adjustments of thepotential of the first. anode electrode 28, as well as adjustments inthe strength of the focusing field of coil 30 willbring the electrons ofthe beam. 20 to a well defined point on the surface of target vl8.

The electron beam 20 maybe causedwto' scan, over the surface of targetl8 in any desired pate tern or raster. However, in tubes ofthistype, theconventional scanning consists of parallel lines from top to the bottomof screen, scanningof the beam is produced by scanning fieldsestablished by two pairs of scanning-coilsrepresented, in Figs. 1 and2,.by neck yoke ,.40. Each pair of coils is connected toappropriate;circuits producing appropriate saw-tooth voltages for providing bothline and frame scansion. of the beam". Such circuits andsystemsmrQvidlng beam scansion are well known in thelartand are notdescribed further in thiscase.-;,,,.'1hese; systems and circuits do notconstitute, apart of this invention. .3

The screen structure used .in the tube shown in Figs. 1 and 2 is similarto that illustrated-and described in the co-pending application SerialNo. 762,175, filed July 19, 1947, of Alfred .N. Gold-1. smith, citedabove. In Figs. 1, 3 and 4 screen structure I8 is shown as constitutinga masking electrode 44 positioned in front of atransparent, phosphorsupporting sheet 48. The masking, electrode 44 is formed from thinmetallic. foil which is opaque to the electrons of the beam IS. Aplurality of apertures 48 are formed through the metal foil of themasking electrode 44 for. the passage therethrough of the electron beam.Supported on the surface of the transparent plate 46 are areas 50 ofphosphor coating which are positioned in the path of the beam- 20passing through apertures 48. 1

It is to be noted in the detailed'drawings of Figs. 3 and 4 that if theelectron beam approaches the target from any one of the directions indiscated asX, Y or Z, the electrons of the beam will pass through theapertures of thetarget-and strike those phosphor spots which are-inline-with the beam path coincident with these directions, As forexample, in Figs. 2 and 3, it -is showiilby way of illustration, thatthe beam approaching thetarget surface along a path X which -is at anangle to the target surface; will pass through and strike only thosephosphor coated spotsindicated b R, which may, for example, luminescewith'a' red light. In a similar manner;- the electrons of the beam"approaching the target along a path Y" will pass through thea'pertures48 of the mask 44 and strike only 'those areas indicated by the lettersG which may, for examplegluminesce with a green light. If the tube is athree color tube, the electrons of the beam appreaching the target alonga path Z will pass thro ah the apertures-44 and strike those phos- D 0areas indicated by the letter B, which may be thoseluminescing with ablue-colored light.

' Means are provided to produce an electron beam which can be properlycontrolled and directed to producethe desired color effects on a screenof .the.type described above. As shown in detail in rfiglzrthe electronbeam first passes through the aperture .of the control grid 24 and intothe aperturedthlmble constituting the screen grid 26. Dueto theconfiguration of the electrostatic field between the. cathode, thecontrol grid and the scre engrid, the electrons form a beamsubstantiallyas shown in Fig. 2. The electrons from the cathode surfacefirst form and pass through a point of. minimum cross-sectional area ora crossover point 25 in this region. From the cross-over point'25', theelectrons of the beam are essentiallydiverging. The beam passes into thefirst anode electrode 28', where it strikes two apertured plate portions52 and 54, which shave off the outer, more divergent. portions of thebeam and limit the beam essentially to the less divergent electrons atthe center or core of the beam. Passing from the first anode electrode28, the electrons meet a converging electrostatic lens field between thefirst anode 28 and the second anode coating 38. ,By adjusting thevoltage of electrode 28, it is possible tocause the electrons ofthe beamto reconverge to a cross-over point 56, shown in Figure 2. The beamafter passing through the cross-over .point 56 is again divergent. Thefocusing field of coil 34 is adjusted to converge the paths of theelectrons of beam 20, so that the beam is brought a, fine focus-spot onthe surface of target l8. 'As is well known in the art, the optics ofthe several electron lenses described as well as that of coil 34, isanalogous to that of light optics. When, by adjustment, the beam isbrought to a fine focus point on target l8, actually the cross-overpoint 55 of the beam is being imaged on the target surface.

' Means are also provided to cause the electron beam 20 to approach thetarget 18 from the requisite direction so that the beam will passthrough apertures 48 .of screen l8 and strike selected phos- 'phor.spots 50. To provide such an effect, the electron beam 20 is given arotational movement by a magnetic field established between the firstanode electrode 28 and the focusing coil 34. This beam rotating fieldmay be produced, for example. by'tw'o'pairs of coils arranged in a neckyoke structure 50, Each pair of coils will produce a field transverse tothe beam path 20 and perpendicular to the tube axis and to the directionof the otherfleld. The two pairs of coils are connected to appropriatevoltage sources of a type, for example, which will cause to flow throughthe tons-' current pulses having a sine wave configuration. The currentpulses flowing through one pair of coils are set to be 90 degrees out ofphase with the current flow through the other pair. Such a system iswell known and will produce a rotational or conical scanningof theelectron'jbeam 20. .When theelectron beam passes through, the constantlyrotating field of coils 60., it is"'as a dire'ctrix forming a conicalsurface.) .Figurez discloses an effect of the. rotational fieldproduced'by the coils, in which the beam isdlsplaced upwardly from itsnormal path along lthe'axis of the tube. The beam in leaving therotating field of coils 60 passes into the focusing field of the coil34. As is well known in the art, an electron beam passing through a lensfield. is acted upon in a manner to cause all portions of the beamdiverging from the field axis to be brought back to a focus point beyondthe lens field. Thus, when the beam 20 is given a displacement from thefield axis of coil 34, in the direction shown in Figure 2, the beam isredirected back toward the field axis by the field of coil 34.Furthermore, the individual electrons of the beam are acted upon to takepaths, which will converge to a point of focus on the field axis. Thefocusing field of coil 34 thus has two functions, first, that offocusing the individual electrons of the beam to a common focus point onthe screen l8; and second, the function of directing the electron beam20 back to the field axis after it has been displaced from the axis bythe rotating fields of coils 60.

Thus, the combined effects of the rotating field of coils 60 and that ofthe focusing coil 34 results in beam 20 being first displaced from itsnormal path and then redirected along a new path to strike the surfaceof target l8 at an angle and sequentially from different directions.

In order that the focusing coil 34 simultaneously perform the twooperations described above, and in the manner described, certainconditions are necessary. So that the beam be focused to a fine spot itis necessary that the cross-over point 56 of the beam be imaged on thescreen l8. It is obvious that if any other portion of the beam having alarger cross-sectional area than the cross-over point 56 were focused orimaged on screen l8, the image spot would be larger and thus pictureresolution of the'tube would be reduced. It is to be noted, however,that, as shown in Figure 2, the crossover point 56 is displaced from thefield axis of focusing coil 34 and that during tube operation, thecross-over point 56 will describe a circular path about the field axis.This condition results since the beam takes a curved path from theelectron gun axis into the rotating field of coil 60. Due to this curvedpath, the beam in entering the field of focusing coil 34 appears to comefrom a virtual cross-over point 62 on the tube axis, as indicated by thedotted projection backward of the beam to point 62. Since the virtualcross-over point 62 is the object point seen-by the field of coil 34 andthis point is on the field axis, the beam will then be directed back tothe axis at the screen.

Also, because of the fact that the'field of coil 34 images a virtualpoint 62, it is necessary that the cross-over point 56 be within therotating field of coils 60 and in a position that the ,virtualcross-over point 62 will remain on. the axis of the focusing field 34.If the cross-over point 56 were not within the field of coils 60, it canbe seen that, when beam 20 passes through the rotating field of coils60, and into the focusing field of coil 34, the virtual cross-over point62, would not remain on the axis of the field.- Because of this reason,then, the focus spot on target l8 would trace a circle. Thus, thecrossover point 56 must lie within the rotating field of coil 60 andthus be displaced from the axis ofthefocusing field 34, in order thatthe .vir tual crossover point 62 lie on the field axis. As can beseen'from Figure 1, thebeam 20.will always be deflected by the scanningfield of coils 40 from points forming an arcuate area about the axis of.tube neck l4. The approximate cenalways form an ter of this area ofdeflection may be indicated by a point 4|, which can be considered asthe center of beam deflection. The beam then will angle with a line N"joining thiscentr of deflection 4| with the point of beam impact ontarget l8 and as shown in the figure. tual point of beam deflection isalways spaced from this center of deflection.

The phosphor screen shown partially in Figures 3 and 4 is one which hasbeen successfully demonstrated in a tube of the type of Figure l. Theapertures 48 are circular openings spaced in parallel lines forming arectangular area or raster on plate 44. The phosphor coatings 50 on thesupport plate 46 are small dots of phosphor material spaced from thepoint of intersection of the line N" passing through the center of eachaperture with plate 46 and arranged 120 degrees about this point ofintersection. For each aperture 48 there are, thus, three phosphor spots50, arranged as described. The spacing between plates 44 and 4B aredetermined by the angle of beam approach and the spacing desired betweenthe phosphor spots 50. A tube of the type described for Figures 1 and 2can be used with any type of simultaneous color television system. inwhich the video signals, corresponding to different colors, follow eachother successively and are applied in sequence to the control grid 24 ofthe tube to modulate the beam 20.

In the successfully operated tube described above, sequential videosignals corresponding to the three primary colors, red, blue and greenwere applied to the control grid 24 to modulate beam 20. The voltages,applied to coils (in forming the rotating field, were synchronized withthe sequence of the incoming video signals so that the beam 20 wasmodulated for one of the three colors at a point in beam rotation 120degrees from its position when modulated by the voltages correspondingto the other two colors. That is, for example, in the position of thebeam in Figure 2, where the beam is shown to be displaced in an upwarddirection from the field axis, the beam could be simultaneouslymodulated with an incoming video signal applied to control grid 24 andcorresponding to a particular color to be reproduced as for example,blue.

As the beam continues in its rotational move-- ment, and reaches a point120 degrees in rotation from its position shown in Figure 2, the beamcould be modulated by a video signal corresponding to a second color tobe reproduced, as for example, green; while the beam in a third position120 degrees spaced from the first and second positions could be againmodulated by signals corresponding to the color red to be reproduced.

In actual operation, cut all pulses are applied to the cathode 22 to cutoff the beam between these three positions, so that the chance of colormixing at the screen is eliminated. The beam thus strikes target iii ina series of short bursts, each of which will pass through the apertures48 of the masking electrode 44 from a different angle, in order tostrike the phosphor. spot 50 corresponding to the color modulation givento the beam. Thus, for example, the beam, in its position shown inFigure 2, where it has been displaced by the rotating field of coil 60to a path above the field axis, will approach the target at a smallangle to the line N which in actual tube operation has been found to bein Thisrresults from the fact that the acthe order oione degree. Asshown iii Figure 3, the beam in this position will approach target l8along the directional path Z and will pass through an aperture andstrike ,a phosphor spot represented by B," in order to produce a visibleblue luminescence. In a similar manner. the beam approaching the targetsurface from the two directions Y and X spaced 'degrees apart will passthrough the apertures 48 to strike successively phosphor spots giving agreen and red luminescent light.

The operation of the tube described, in Fi ures 1 and 3, need not belimited. to a type of beam commutation provided by the cut-off pulsesapplied to control grid 24, but there may be also used an aperturedelectrode positioned between the screen 18 and the rotating fields 60 asdisclosed in the above-mentioned copending application of R. R. Law. Inthis modification, the apertured electrode comprises arcuate aperturesequally spaced 120 degrees apart from the center of the electrode. Thebeam then is mechanically cut off between apertures and passes throughthe apertures as short bursts which are then brought by the field ofcoil 34 to the target surface from the three different directions.

The operation of the tube described has been that in which sequentialcolor signals are applied to the control grid 24 for modulating theelectron beam. The time of the sequential picture signals may be of anyappropriate length. For example, in the successfully operated tubedescribed above, the picture signals were applied sequentially forapicture element time, so that, as the beam scanned a line across thetarget surface, red, green and blue fluorescing dots were activated insuccession. The elemental period of time is that determined by the timethe beam scans one line across the target divided by the number of alsobe used with a system providing sequential,

line scanning or sequential frame scanning in which respectively thebeam scans across the target in one line and strikes only the phosphorspots luminescing with a single color or scans a whole frame to producea single color. In any of the above-described systems which are used, itis obvious that the rotating field of coils 60 must be synchronized withthe sequential color video signals applied to the control grid, and alsoif cut off pulses are used, such pulses must correspond in time sequenceto the sequential system used.

A target similar to that indicated in Figures 3 and 4, may also beproduced by making the phosphor areas .R, G and 3" as parallel stripsextending horizontally across the surface of the target support plate46. Furthermore, the masking screen may be one in which the apertures 48are also parallel to each other and to the phosphor strips on thesurface of plate 46. If the target 18 is of such a form, it is obviousthat the apertures 48 cannot be spaced apart less than the Width ofthree of the color strips placed on the supporting plate 46.Furthermore, the spacing of th masking foil 44 from support plate 46 aswell as the spacing of thecolofstrips themselves from each other arelimited by the simple"- -The above described details of the target areby way of illustration of the target structure which can be used withthe tube of Figure 1.

Another type of target structure which may be used with tubes similar tothat described above and illustrated in Figures 1 through 4 are those,not using a masking electrode, but consisting principally of cellularstructure. A screen of this type is shown in Figure 5 in which theelemental portions of the target, which are of picture element size,consist of tubular members having a triangular cross-sectional area. Thetubular members 10 are similarly arranged, as shown in Figure 5, inparallel rows, which are preferably positioned within the tube parallelto the line scanning direction of the electron beam. The spaces betweenthe tubular members 10, which do not have the same positionedarrangement, are filled or covered to provide screen portions opaque tothe electron beam. The inner surfaces of the triangular tubular members'10 are coated with different phosphors, each inner face of each tubularmember being coated with a different phosphor.

The screen structure shown in Figure 5 is used with the tube describedin Figures 1 and 2 in which, as described above, the beam is caused toapproach the target from a plurality of dif-- ferent directions X, Y andZ. In the tube using the screen of Figure 5, these directions of beamapproach to the target are selected so that the beam approaching alongany one of the directions will strike only one inner face of eachtubular cell 10. As shown in Figure 5, the beam approaching the targetscreen from the direction X is caused to strike an inner surface of eachcell III, which is coated with a phosphor R having a red fluorescence.In like manner, the beam \striking the target from direction Y and Zwill strike the inner surfaces of each cell 10 which are respectivelycoated with phosphors G and B, luminescing respectively with a green andblue light.

The screen of Figure 5 described above has some advantages over thatdescribed in Figures 1 through 4 as well as some disadvantages. Forexample, the screen of Figure 5 does not necessitate the use of amasking electrode so that the phosphor area of the screen is struck byall of the beam, to provide greater luminescence. However, since thephosphor surfaces of the screen of Figure 5 are parallel to the line ofvision of an observer, the total light output from the screen can not befully realized. Thus, screens of the type of Figure 5 have actuallyshown less brilliance and light response than those of the type shown inFigures 1 through 4.

While certain specific embodiments have been illustrated and described,it will be understood that various changes and modifications may be madetherein without departing from the spirit and scope of the invention.

What is claimed is:

1. An electron discharge device comprising, an electron gun means forforming a beam of electrons along a normal path, a target electrodepositioned transversely to said beam path, means for scanning said beamover a surface of said target, a. phosphor coating on portions of saidtarget surface, each of said coated portions being responsive tospecific directions of beam approach, means between said gun and saidtarget electrode for producing a beam deflecting field transverse tosaid beam path, a first focusing means for bringing the electrons ofsaid beam between said target and said beam deflecting means forimagingsaid cross-over point on said target surface and for returning said beamto its normal path at an angle thereto.

2. An electron discharge device comprising, an electron gun meansincluding an electron source for forming a beam of electrons along anormal path, a targetelectrode having a portion positioned transverselyto said beam path, a phosphor coating on a plurality of areas of saidtarget portion, a first beam focusing means between said electron sourceand said target electrode for bringing the electrons of said beam to across-over point spaced from said target electrode, a second beamfocusing means between said first beam focusing means and said targetelectrode for imaging said cross-over point on said target portion, andmeans for providing a beam deflecting field in the region of saidcrossover point for displacing said beam from its normal path, wherebysaid beam approaches said target from a plurality pf directions, saidtarget electrode including an apertured structure positioned betweensaid target portion and said electron gun to mask each of said phosphorcoated target areas from all but one of said plurality of directions ofbeam approach.

3. An electron discharge device comprising, an electron gun meansincluding an electron source for forming a beam of electrons along anormal path, a target electrode having a portion positioned transverselyto said beam path, a phosphor coating on a plurality of areas of saidtarget portion, a first beam focusing means between said electron sourceand said target electrode for bringing the electrons of said beam to across-over point spaced from said target electrode, a second beamfocusing means between said first beam focusing means and said targetelectrode for imaging said cross-over point on said target portion, andfield producing means for displacing said beam along a plurality ofpaths off-set from said normal beam path, whereby said beam approachessaid target from a plurality of directions, said target electrodeincluding an apertured structure positioned between said target portionand said electron gun to mask each of said phosphor coated target areasfrom all but one of said plurality of directions of beam approach.

4. An electron discharge device comprising, an electron gun meansincluding an electron source for forming a beam of electrons along anormal path, a target electrode having a portion positioned transverselyto said beam path, a phosphor coating on a plurality of areas of saidtarget portion, a first beam focusing means between said electron sourceand said target electrode for bringing the electrons of said beamto across-over point spaced from said target electrode, a second beamfocusing means between said first beam focusing means and said targetelectrode for imaging said cross-over point on said target portion, andfield producing means for displacing said beam along a plurality ofpaths off-set at equal angular spacings from said normal beam path,whereby said beam approaches said target from a plurality of directions,said target electrode including structure positioned to mask each ofsaid phosphor coated target areas from all but one of said plurality ofdirections of beam approach.

5. An electron discharge device comprising, an

electron gun means including an electron source ii for forming a beam ofelectrons along a normal path, a target electrode having a portionpositioned transversely to said beam path, a phosphor coating on aplurality of areas of said'target portion, a, first beam focusing meansbetween said electron source and said target electrode for bringing 'theelectrons of said beam to a crossover point spaced from saidtargetelectrode, a second beam focusing means between said first beamfocusing means and said target electrode for imaging said cross-overpoint on said target portion, and means for providing a rotating fieldin the region of said cross-over point for displacing said beam along aplurality of paths offq set from said normal beam path, whereby saidbeamapproaches said target from a plurality of directions, said targetelectrode including an apertured structure positioned between saidtarget portions and said electron gun to mask each of said phosphorcoated target areas from all but one of said plurality of directions ofbeam approach.

6. An electron discharge device comprising, an electron gun meansincluding an electron source for forming a beam of electrons along anormal path, a target electrode having a portion positioned transverselyto said beam path, a phosphor coating on. a plurality of areas of saidtarget portion,

a first beam focusing means between said electron source and said targetelectrode for bringing the electrons of said beam to a cross-over pointspaced from said target electrode, a second beam focusing means betweensaid first beam focusing means and said target electrode for imagingsaid cross-over point on said target portion, and a coil surroundingsaid beam path for providing a rotating field in the region of saidcross-over point for displacing said beam along a plurality of pathsoff-set from said normal beam path, whereby said beam approaches saidtarget from a plurality of direc-' tions, said target electrodeincluding an apertured structure positioned between said target portionsand said electron gun to mask each of said phosphor coated target areasfrom all but one of said plurality of directions of beam approach.

7. An electron discharge device comprising. an electron gun means forforming a beam of electrons along a normal path, a target electrodepositioned transversely of said'beam path, said target electrode havinga plurality of surfaces divided into series with the. surfaces of. eachseries facing substantially the same direction different from thedirection faced by the other series. a first focusing means for bringingthe electrons of said beam to a cross-over point spaced from said targetelectrode, a second focusing means between said first focusing means andsaid target for impinging said cross-over point on said target and abeam deflecting means between said flrst and second focusing means fordisplacing said beam from its. normal path, whereby said beam approachessaid target from said different directions.

8. An electron discharge device comprising, an electron gun means forforming a beam of electrons along a normal path, a target electrodepositioned transversely to said beam path, said target electrode havinga plurality of surfaces divided into series with the surfaces of eachseries facing substantially the same direction different from thedirection faced by the other series, a' first focusing means forbringing the electrons of said beam to a cross-over point spaced fromsaid target electrode, a second focusing means between said firstfocusing means and said target for imaging said cross-over point on saidtarget and means for providing a bearndefleeting field in the region ofsaid cross-over pointfor displacing said beam from its normal path,whereby said beam approaches saidtarget from said diiferent directions.DIETRICH A. JENNY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,197,523 Gabor Apr. 16, 19402,446,249 Schroeder Aug. 3, 1948 2,446,440 Swedlund Aug. 3, 19482,446,791 Schroeder Aug. 10, 1948 2,480,848 Geer Sept. 6, 1949 2,481,839Goldsmith Sept. 13, 1949. 2,498,705 Parker Feb. 28, 1950

